Teen Sex May Affect Brain Development, Study Suggests

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The uproar that followed a November episode of Fox's "Glee" in
which two teen couples had sex for the first time may have some
scientific legs. New research shows sex during the adolescent
years could affect mood and brain development into
adulthood.

The study, which was carried out on hamsters, reveals how social
experiences during adolescence when
the brain is still developing can have broad consequences,
say the researchers from Ohio State University College of
Medicine.

Specifically, the animals that mated earlier in life had higher
levels of depressive behaviors, changes to the brain and smaller
reproductive tissues compared to those that had intercourse later
or not at all.

"Having a sexual experience during this time point, early in
life, is not without consequence," study co-author John Morris, a
doctoral student in psychology at Ohio State, said in a
statement.

Morris and his colleagues cautioned, however, that the study
should not be used to promote
teenage abstinence, as they noted the research was carried
out on hamsters and it isn't certain the same conclusion will
hold for humans. As such, more research is needed understand the
effects of sex during puberty.

The study, which was presented on Nov. 15 at the Society for
Neuroscience annual meeting, has yet to be peer-reviewed for
acceptance in a scientific journal.

The researchers had a group of 40-day-old male hamsters (the
equivalent of human teens) mate with adult females in heat. A
second group of males mated in adulthood (80 days into life),
while a control group was not exposed to females. Hamsters reach
puberty at 21 days, and by 40 days have reached late- to
post-adolescence, roughly equivalent to ages 16 to 20 in humans,
said study researcher Randy Nelson, neuroscience professor and
chair at Ohio State.

Researchers did various tests on the hamsters at 120 days.

When placed in water, the animals that had sex at 40 days were
more likely to stop swimming vigorously, a symptom of depression,
than the other three groups. All of the sexually active hamsters
showed higher levels of anxiety, measured by willingness to
explore a maze, than the virgin hamsters.

The group that had sex in adolescence also showed less complexity
in the brain's dendrites, thebranching extensions of neurons that
receive messages from other nerve cells, and higher expression of
a gene associated with inflammation. Certain reproductive
tissues, including the
seminal vesicles (glands in males that secrete ejaculate) and
vas deferens (tube that carries sperm out of the testes), were
also smaller in these animals. [ 5 Myths
About the Male Body ]

The 40-day group also showed some benefits of early life sexual
experience, the researchers said, including reduced body mass and
enhanced immune responses in adulthood.

Hormones plus experience

"We used the opportunity to have sex, which naturally increases
testosterone levels, to see whether these experiences during
early life would have long-term consequence," co-author Zachary
Weil, a research assistant professor of neuroscience at Ohio
State, told LiveScience. "Previous animal studies have shown that
experiences and
sex hormones when administered early in life have long-term
consequences for physiology, brain and behavior."

The researchers based their study on work by Cheryl Sisk at
Michigan State University that showed that, in rodents, the
elevated testosterone levels in puberty influence the development
of brain circuits that underlie
male social behaviors. In Sisk's study, castrated hamsters
were less likely to mate with receptive females and were more
submissive toward male intruders compared with males that had
natural levels of testosterone. Replacing the hormone in
adulthood did not restore normal levels of these social
behaviors.

"We think that pubertal testosterone organizes neural circuits
during adolescence in a way that maximizes male-typical social
responses and behaviors in adulthood," said Sisk, who was not
involved in the current study. She added that testosterone may be
linked to structural changes in the brain, including how the
dendrites are organized or connected to one another.

Weil's team is now researching whether testosterone is the sole
mechanism. In a new study, the animals will be given the hormone
rather than allowed to mate.

Sisk said she believes that a combination of hormones and
experiences affect brain development during puberty and
adolescence. "In humans, these two variables are hard to tease
apart, because the elevated hormone levels that are typical of
puberty lead to the appearance of secondary sex characteristics,
which in turn changes the nature of interactions with parents,
peers and teachers," she said.

In response to the "virgin sex" on "Glee," the Parents Television
Council, a watchdog group, denounced the episode in a statement
before it aired, saying,"The fact that 'Glee' intends to ...
celebrate children having sex is reprehensible." While the new
study can't argue for or against this statement, its results
suggest more discussion is needed on how early experiences impact
adulthood, the researchers say.

"These results are very preliminary and should be used only to
stimulate discussion about the role of early life experiences in
humans in a general way," Weil said.

Thirteen percent of 15-year-olds in the U.S. have had
heterosexual sex, according to the Centers for Disease Control
and Prevention, and the average age for first-time intercourse is
17 — well within the equivalent age for the new study. "There is
previous evidence that the age of
first sexual experiences correlates with mental health issues
in humans," Weil said. "But with all human research, there are a
number of other variables involved, such as parental supervision
and socioeconomic status, that may be involved with both the age
of first experience and depression." [ 10
Surprising Sex Statistics ]

Although his team's work may be useful in beginning to understand
the physical and mental health outcomes of adolescent
sex in humans, Weil said the key finding of the study is that
experience during adolescence, when the brain is still
developing, can have long-term effects on health and behavior. He
cautioned against direct correlations with humans.

"In no way do these data bear directly on the issue of teenage
abstinence," Weil stressed. "Much more research needs to be done
in both human and animal models to understand how these types of
experiences translate into changes in mood and physiology."

Weil said the data does, however, indicate how potentially
damaging neglect and abuse of young people can be, in which both
heightened hormones and negative experiences are at work.